1. Field of the Invention
The present invention relates to an optical device composed of a substrate and a light emitting layer formed on the front surface of the substrate and also to a manufacturing method for the optical device.
2. Description of the Related Art
In a fabrication process for an optical device such as a laser diode (LD) and a light emitting diode (LED), a light emitting layer (epitaxial layer) is formed by epitaxial growth, for example, on the upper surface (front surface) of a crystal growing substrate of sapphire, SiC, or the like, thereby manufacturing an optical device wafer for forming a plurality of optical devices. The light emitting layer formed on the crystal growing substrate of the optical device wafer is partitioned by a plurality of crossing division lines to define a plurality of separate regions where the plural optical devices such as LDs and LEDs are respectively formed. The optical device wafer is divided along these division lines to obtain the individual optical devices as chips.
As a method of dividing the optical device wafer along the division lines, there are known methods as described in Japanese Patent Laid-open Nos. Hei 10-305420 and 2008-006492. The dividing method described in Japanese Patent Laid-open No. Hei 10-305420 includes the steps of applying a pulsed laser beam having an absorption wavelength to the wafer along the division lines to form a laser processed groove along each division line by ablation and next applying an external force to the wafer to thereby break the wafer along each division line where the laser processed groove is formed as a division start point.
On the other hand, the dividing method described in Japanese Patent Laid-open No. 2008-006492 is intended to improve the luminance of the optical device and it includes the steps of applying a pulsed laser beam having a transmission wavelength to the wafer along the division lines in the condition where the focal point of the pulsed laser beam is set inside the wafer, thereby forming a modified layer inside the wafer along each division line and next applying an external force to each division line where the modified layer is formed to be reduced in strength, thereby dividing the wafer along each division line.